atmosphere, they're known to change
in value. This doesn't usually keep the
radio from working, but it won't be
performing at its best with wrong-value resistors. The color codes have
the same meaning as they do today,
but they're read a little differently:
The "body" of the capacitor — the
largest color section — is the first
digit. The "tip" or color band at one
edge of the component is the second
digit, and the "dot" — or color band —
in the center of the body color is the
multiplier. Shown in Photo 11, this
100K ohm resistor (
brown-black-yellow) is within 20% of its marked
value, so doesn't need any further
action. I checked a handful of others
and they were in spec, so in this
case, none needed to be replaced.
That's actually pretty rare. I've run
into resistors which had drifted to
over 100% of their marked value.
You can still get new
manufactured carbon composition
resistors, although they're a bit more
expensive than other types. Visually,
they're a different style, looking
similar to modern resistors, but those
did start turning up in the late '30s.
You'd have to replace every one if
you wanted a uniform look. It's
possible, just a ton of work.
There's not a whole lot more to
say about this step. It took about an
hour and a half to swap out the
components, and now it's ready for
the first power-up (Photo 12)!
I've double-checked my work to
make sure no leads are touching
which could cause a short, and
reinstalled the tubes and ballast.
Now, for the obligatory safety
warnings: If you're working with a
radio that uses a power transformer,
it's fine to connect directly to the
mains at this point. For a
De Wald, however, you absolutely
must use an isolation transformer or
you risk a deadly electric shock.
The radio's metal parts could
52 June 2015
Photo 10. Further along, with jumpers to keep track of parts I've removed
to get to the ones below.
Photo 11. Measuring the drift on a
nominal 100K ohm resistor.
Photo 9. Starting to replace the old caps.